The present invention relates to a radiation-sensitive mixture, a recording material produced therewith and also to a process for producing heat-resistant and chemical-resistant relief copies using the recording material. The invention is based on a positive-working radiation-sensitive or photosensitive mixture containing:
(a) a water-insoluble polymeric binder which is soluble in aqueous/alkaline solutions, and PA1 (b) a 1,2-quinone diazide and/or a combination of PA1 (1) a water-insoluble polymeric binder which is soluble in aqueous alkaline solutions, and PA1 (2) at least one of a 1,2-quinone diazide and a combination of
a compound which forms strong acid when exposed to actinic radiation, and PA2 a compound containing at least one clearable C--O--C bond as essential constituents. PA2 a compound which forms strong acid when exposed to actinic radiation, and PA2 a compound containing at least one acid-clearable C--O--C bond,
Positive-working photosensitive mixtures, i.e., mixtures of the constituents mentioned in which a copying layer, becomes soluble in the areas exposed to light, are known and have been described for a wide variety of possible applications, such as for producing lithographic plates or photoresists.
A substantial proportion of the properties of these copying layers is determined by the quantitative main constituent of the radiation-sensitive or photosensitive mixture, the binder. The binders used for positive copying layers are virtually exclusively phenol/formaldehyde or cresol/formaldehyde condensation products of the novolak type. For some applications of positive copying layers, however, the resulting properties are still not ideal. This relates, in particular, to the heat resistance in the case of photoresist applications and the length of the print runs when used as lithographic plates.
It has been found that substitution of the novolaks by binders having a higher glass transition temperature results in a generally better property profile. Thus, a whole series of alkali-soluble binders have been described for positive copying layers such as, for example, naphthol-based phenolic resins (U.S. Pat. No. 4,551,409), homopolymers and copolymers of vinylphenols (DE 2,322,230, corresponding to U.S. Pat. No. 3,869,292 and DE 3,406,927, corresponding to U.S. Pat. No. 4,678,737), polymers of the esters of acrylic acids with phenols (Japanese Published Specification 76/36129, EP 212,440 and EP 212,439) or copolymers of hydroxyphenylmaleimides (EP 187,517).
Binders of the type mentioned have not hitherto been able, however, to find practical application. One reason for this is that these polymers do not satisfactorily fulfill an essential requirement imposed on binders of positive copying layers, that of the possibility of thermal self-crosslinking. This property, which exists in the case of novolaks, is of importance if the copying layer is to withstand aggressive chemicals.
DE 3,820,699 describes polymers based on hydroxybenzylacrylamides which fulfill the requirement for crosslinkable alkali-soluble monomeric components. It is disadvantageous, however, that the polymer can contain these monomers only in a limited amount since otherwise photosensitivity and development behavior are unfavorably affected.
It is also known to incorporate units in the polymers which, although they are not alkali-soluble, make possible thermal crosslinking, such as the polymers, described in EP 184,044, corresponding to U.S. Pat. No. 4,699,867, containing crosslinkable --CH.sub.2 --OR units, where R is hydrogen, or alkyl or acyl groups. However, these units also impair the development behavior if they are contained in the polymers in the amounts necessary for a reliable thermal postcuring.